This blog provides updated forecasts and comments on current weather or other topics

Thursday, January 19, 2012

Ice Storm: Freezing Rain and Sleet

From a bit of weather overload, I decided to take a break from this blog for a while, but the interest and importance of what is happening now is bringing me back online (and UW classes are cancelled so I don't have to be in class for my real job).

Over the past day and particularly this morning, something relatively unusual and, quite frankly, dangerous is going on outside--a freezing rain/sleet storm--and let me talk about it a bit.

I was woken up this morning by the sound of sleet (ice pellets) banging on my window. Walking outside, there were ice pellets falling and the snow had a thin crust on it. Yesterday, after the main snow, there was light freezing drizzle (and for some very small ice pellets) over much of the area.

This is a highly unusual situation here in western Washington: outside of the famous ice storms of the western Columbia Gorge (also known as the silver thaw), western Washington does not get freezing rain very often. The last big event was over the southern Sound in December 1996, when Sea Tac airport closed. The airport is closed right now

Why is this happening?

Right now a warm front is to our south, with temperatures in the 50s in the Willamette Valley, while north of Olympia temperatures are below freezing:
.

Yesterday, after the main action was over, we were left with a saturated lower atmosphere in which there was supercooled clouds---water droplet clouds that were below freezing through their entire depth. Yes, believe it or not liquid water can exist below freezing (typically in clean air from 0 to roughly -15C). Some of this cloud water was converted into freezing rain. Usual for us to see that.

But there is another way to get freezing rain (and sleet too): when warm air pushes in above a sub-freezing air mass near the surface. And that is happening right now.

Here is the temperature variation above Seattle now from the profiler located at the National Weather Service office at Sand Point.

Cool air at the surface, but then a rapid warming (an inversion) above 400 meters (temps in C--really something called virtual temperature--subtract about 1 for air temperature. The warm air (and southwesterly winds) have moved in aloft--a typical warm frontal structure (see graphic):

The precipitation area is reaching roughly to Everett based on the weather radar (see radar below).

Over the northern part of the domain the southwesterly air is high enough so that it is below freezing, so there is snow (Everett is snowing). But farther south, we have above-freezing air aloft and rain. Rain that is falling into below-freezing air. Some of this rain is freezing on the way down into ice pellets or sleet (what woke me up), but a lot of it is staying liquid and hitting the ground as freezing rain...which freezes on contact with the cold surface. The current freezing rain is a mixture of the two icing mechanisms (freezing drizzle from shallow clouds and freezing rain from aloft)

Dangerous stuff, that freezing rain. Not good for driving. I just noticed my colleagues at the National Weather Service have an ice storm warning out. Of course, this freezing rain/drizzle is on top of roadways that melted yesterday and then refroze. And here is the weather icon the NWS used for our weather this morning. You see an icon like that and you worry.

Anyway, today there will be wintry mix--freezing rain, ice pellets/sleet, snow, rain until the air warms up enough aloft to turn it all to rain (probably by later this afternoon)

For those of you who like to geek out on cool technology, here is the correlation map from the dual pol capability of the Camano Island weather radar. The pink indicates relatively uniform conditions an farther (and higher) out that indicates snow. Closer in (lower) you see reds and yellow. That is indicating melting snow and a mixture of snow, melting snow, and rain.

NORTHWEST WEATHER WORKSHOP:The Pacific Northwest Weather Workshop, the main annual gathering for those interested in Northwest weather and climate, will be held on March 2-3, 2012 at the NOAA Sand Point facility in Seattle. For more information and to register please check the meeting web site: http://www.atmos.washington.edu/pnww/http://www.atmos.washington.edu/pnww/

Would just like to say I check your blog before I do any other news station. I have been out of college for two years...and I just felt like I was in a classrooom. Great feeling! Thanks for the mini lecture and all of your work!

I recall an ice storm back in around 2002 or 2003 that hit in the Skykomish Valley... we got about 1/2" in Snohomish at the time. At the time there were tree farms for the paper mills along Hwy 2 between Snohomish and Monroe, and those trees were all just bent over with their tops touching the ground. Incredible. Last night, I was driving in downtown Monroe in the freezing drizzle around 5:30 p.m. - my windshield was freezing as I was driving, so I turned back and came home. This morning, it's snowing again - looks like we've got another couple of inches so far here, 3 miles N of Monroe, 400' Elevation. Thank you so much for your blog!!!

Hi Cliff,Thanks for your posts. They are the most sane and rational of all the other stuff out there.Any chance of giving more explanation of what happened yesterday? I assumed it was warmer and rain aloft freezing with the colder air at the surface. But I've never heard of super cooled clouds containing liquid water. I've always assumed if cloud temp is below 32, then it falls as snow.

I remember several ice storms on Long Island (NY) when I was growing up--waking up to find every blade of grass, every tree, everything encased in a quarter-inch of ice, with the sun shining and everything glittering with diamonds. Stunningly beautiful and wickedly dangerous.

Wow. Thank you for the update - so much more interesting than camera angles directed at the ground and news people pointing at it and rubbing it and saying, "Look! Ice!" I do hope you found your dog too.

Thanks Cliff for your intelligent and level-headed reports, yours is the first I got to in the morning! Hoping the ice eases up later today, do you think it may warm up a bit by early afternoon? I am starting to get cabin fever!

2 miles S of Hansville 300ft elev, 2 1/2" snow Tuesday, about the same yesterday -- so far this morning about a 1/4 inch or so of snow that seems to periodically change to sleet or freezing rain. Temperature is 27F (on both of the outdoor thermometers), small icicles have formed on the tips of many small branches and some from the eaves of the house. Ice storm could be just beginning here.

Cliff,With the BLI YZT gradient still at -15.6 mb and increasing slightly, and unlike yesterday, no onshore component, I ask you this;Will the warm front be able to overcome the arctic outflow at the surface?

We have so much snow here in Snohomish (nearly a foot at approx 200' elevation at my house in Fobes) that tomorrow's predicted rain is going to make trees very heavy... I hope we get our predicted 37* high here today so the snow can melt off of the trees & we won't lose power all over the place.

Thanks Cliff for keeping us up-to-date - this competing warm system & cold air have made for an interesting week.

Thanks so much for the hard work, Cliff. I'v seen and heard you all over the TV and radio stations the last few days. You deserve a few days off!! Sleeting in Port Orchard! A hard crust over all the snow. Hard on the puppies' paws.

Thanks for your continued updates! As a UW graduate I miss being in the classroom and learning soooo much! Your blog not only tells the weather, but it tells WHY the weather happens! I have been really enjoying it this whole week. Makes me fell like I am back at UW.

Around 78th and Greenwood we were having freezing rain last night and this morning. The ice was coating all of the windows with a blurry layer. Just a few minutes ago the freezing rain changed over to snow. About to head out on foot, not sure how slick it is yet. Route 5 Metro seems to be going by on Greenwood without too much trouble.

The precipitation is coming in the form of snow at the moment here on Bainbridge Island. I'm wistfully enjoying watching the closing chapter of this fascinating snow event. Thank you for translating weather poetry into weather science.

Snowing in Mukilteo a few hundred feet above sea level, about 3X harder than yesterday. Some tuition about the convergence zone would be awesome! I believe we hold down one end of it and therefore get more/less of what goes on in the rest of the region. Absolutely love your blog! Thank you. CSD

Wow...i don't remember having an ice storm anywhere I lived except New Year's Eve 1978, and unfortunately that is the night our house decided to burn down. We were in Dallas, TX, totally unprepared. I remember waking up with my sister under one of my dad's arm and me under the other. It was epic as far as weather goes and I will never forget it.

It started snowing again in MLT this morning. First we had ice pellets, but now it is just snow. There is ice from last night -about 1.5 cm on top of the snow- and that is now buried. Temperature is about 26. There are power outages in Shoreline.

I remember an ice storm in January 2004 in Seattle. First snow then ice. No power for 3 days.Stay warm and thank you again for the instructive updates.

Oh Cliff, you and your family must be terribly distraught throughout this event. Weather is more exciting when it doesn't carry with it the stress of wondering how your little dog is faring in all this. My heart goes out to you. I hope you find your dog soon.

it's snowing in Ballard/Loyal Heights and it has been for a good hour or two, with accumulation. We probably have another inch or so on the ground since last night (all the tracks, etc are completely covered)

When reading this my first thought was "Hey Seattle turned into Portland!"

yes, freezing rain is very unusual for Seattle, but a good percentage of Portland's snow events are typically preceded or followed by (or both) a freezing rain event, thanks to the east winds that get pulled out of the gorge.

I did a report on the effect that east wind events have on Portland's weather during the winter and my professor's (Dr. Businger) first response was "thats why you move to Seattle"

On Capitol Hill this morning it seemed to be mostly ice pellets, little or no freezing rain. It made walking a little easier than last night, since it gritted up the ice a good bit. As the weather warms a bit today it's going to get slick, when the pellet cover we have now thaws and refreezes. Be careful out there!

Cliff, I really enjoy your blog. Please keep it up. I have learned so much about the weather and how it works from you. Thank you, thank you, thank you. It's interesting to see how different the weather can be in different areas and why. I wish I could take one of your classes at UW to learn more from you. :)

No ice here in Kingston. But snowing vigorously for the last few hours - we've added a few inches to the 6" on the ground from yesterday. Am hoping we go from snow to rain gracefully without ice storms here. Cliff, will we?

I grew up in East Portland and am all too familiar with Silver Thaws. Pretty, but impossible to be out in on foot or car. Unless you are wearing crampons or driving with studs. But then the danger is the idiot who thinks they can drive in these conditions who decides to t-bone you! Or falling tree limbs (or trees themselves!) and power lines and sometimes the heavy ice itself! A 3" in diameter piece of ice a foot long dropping 100' packs quite a whallop!

Speaking of stupidity I tried watching the local affiliate news coverage of this storm. It seems to me that driving a vehicle while a live TV camera is pointed at you and you are talking to that camera is about as or more dangerous as driving while texting - even in good driving conditions - much less the conditions outside right now. This activity is a new level of stupidity exhibited by the local news stations and should probably be outlawed, given the dangers it poses to other drivers and pedestrians. It also sets a really bad example.

On the other hand, I am expecting a few of these to end up on YouTube when they inevitably crash (one reporter did say she drove up onto a curb the day before - yet she was driving and broadcasting; she hadn't learned her lesson). Who knows? Jim Foreman or one of the other Weather Talking Heads could even end up with a Darwin Award for this reckless behavior!

Hi Cliff, I noticed that you enjoy using terms like "SLUSHMAGEDDON" in your (fun!) posts about how Seattle deals with snow and ice. Just for fun, I've been thinking up new ones, and came up with ICECHATON, a twist of "eschaton," the term for the end of the world. Corny? Yeah. But something to do when stuck at home as Seattle endures an ICECHATON! :)

There is an interesting quirk with the Detailed Point Forecast provided by the NWS website . There are three forecast zones that meet in the North Kitsap Peninsula from near Kingston up to Hansville. This can present some potential problems.

Clicking on points that are located on the east side of the peninsula from Kingston nearly all the way to Hansville, there are no warnings whatsoever. One grid square to the west, "Ice Storm Warning" is posted. This part of the peninsula is two grid squares wide from east to west.

I've encountered this a few times before because I live very close to the border between zones. In my case -- I am in the non-warning zone, yet if I click one square north or one square west I see the warnings. My forecast zone is Everett and Vicinity, while immediately north and west is the Hood Canal zone and south of Kingston is the Seattle-Bremerton Zone.

I realize the zones need to have borders somewhere, but here, this great a transition does bother me. Had I just checked my local zone (in my favorites) and not checked your blog and other sources, I may not have known that anywhere I could possibly want to drive to would be within the Ice Storm Warning zone (and I don't usually check the detailed point forecast for locations several miles away). Also, our power and emergency service providers come from the Ice Storm Warning zones.

Something as simple as an alert stating "Adjacent to Warning Area" or "Warning Nearby" would be enough to prompt further investigation.

Help! I am responsible for determining whether or not to cancel an important meeting this evening. We're in Greenlake, with folks coming from the North End, but also West Seattle and Beacon Hill. I'm holding out hope for the thaw....Am I crazy? Should I just go ahead and call it now, or wait until the afternoon? What would be your professional opinion?

Here in Loyal Heights (located between Ballard and Crown Hill) it has mostly been snowing for an hour or two, but now it seems to be mixing with freezing rain also. It was mostly freezing rain earlier in the morning.

The temp is still below 31 degrees, so I don't think we'll get a high temp of 36 degrees today, but I could be wrong. It was colder last night than had been initially predicted by noaa. I have to wonder if it will really warm up all that much tomarrow. Could there still be ice and snow on the ground (and some of the roadways) for most of the day tomarrow?

Don't cancel the meeting...just reschedule it... If you're worried about it now... that's the conservative alternative... and no one can fault you for being careful. Want to see the opposite? Just reference "Italian cruise liner"...

Interesting post, Cliff ~ thank you! Freezing rain is more common up here (north Whatcom County) ~ apparently when the warm air comes in over the icy Fraser Valley blasts we have that "perfect storm". We may face that in the next day or two, but at the moment it's overcast and dry with wind chill still in the single digits. Hoping to feel warmer again soon...

A mix of freezing rain, snow and sleet on top of the 4" of snow we got in Queen Anne. NWS now saying that the temperature won't rise above freezing until tonight. I'm wondering when it'll be warm enough to melt the wintry mix on the roads, and if it's still going to get into the mid-40's tomorrow.

By the way, thanks Cliff, for all of your timely blogging on this. It's been a tremendous help, and it's been fascinating to see the evolving weather, forecasts, and people's reactions to it. Even though the forecasts haven't been perfect, they've been, on the whole, quite accurate, which is a big change from the old snowstorms in 1986 and 1996, which always seemed to take the NWS by surprise.

I, too, hope your dog is okay! Hopefully, she'll be more willing to go inside a building where you can be contacted, and get her.

Had 6-7 inches of snow on south Vashon yesterday. Now have at least 1/2 inch of ice on everything. Branches are cracking off the trees and power keeps going down and coming back on. We should be losing power soon, unfortunately. Hope little Leah finds shelter somewhere. The snow might flush her out where she can be seen more readily.

Cliff, I have recently "discovered" you and am thrilled that I have. You take meterology to a whole new level for the layman. The interesting and detailed information that you provide is unparalled. Thank you! I'm now a huge fan.

Unknown, I would cancel if it were me. I'm on Phinney and we're getting a steady sleety snow. I don't see how the roads will be in good shape by this afternoon even if it does start to rain later today. My guess is that it will take time for the ice to clear up, and freezing slush is dangerous as well. You can always reschedule.

Thank you for your posts, I am new to Seattle from the east coast and am a big fan.In North Cap Hill now it's snowing real snow for the moment.But most importantly, can you tell us if you found your dog? I hope so!

I was wrong, after measuring it myself, we have over 1/2 inch ice on top of everything here in Spanaway and Puyallup area. Its been freezing non stop now since 7am Wednesday morning. Temps still below freezing. Tonight is going to be a lot worse!

I live in Mukilteo near the Harbour Pointe Golf Course.Since Tuesday there have been 9 inches of mostly dry snow.There was 2 inches Saturday and about a half inch Sunday night.What's notable about this is that since the winter of 1998-99 I've gone periodically to Coeur d'Alene in North Idaho-including for Thanksgiving and Christmas. In all that time this is the first time this late in the winter I've seen more snow here-lots more-than there.

Speaking of 1996 and ice storms..I was living in Coeur d'Alene when on Nov.19 we had "Ice Storm '96." People living in outlying areas were without power for weeks. Fortunately I lived just a few blocks from power co.office and was without power for just a few hours.

Good call,Cliff,on what this storm would do,for the most part.I just started getting onto your blogs about Monday. I don't know what I was waiting for.

Over here on the west side of Bainbridge Island, it definitely is not "the end." At 2:45 p.m. on the 19th, we still have white fluffy stuff coming down from the sky. Not rain. Not sleet. S-N-O-W. It has been falling slowly but steadily most of the day and shows no signs of stopping or turning to rain. There is nary a puff of wind, so it seems whatever weather is sitting right over us will be here for a while.